Transformation of polyphase currents into practically constant direct currents



TRAVNsFoRMATIoN or PoLYPHAsE cuREnTs 'INT0 PnAcncALLY consmn umEcT cuRRENTs.

' 'APPLICATION FILED .IAN- l. 1918.

1,390,504. Pawndsepn 13,1921.

2 SHEETS-SHEET I.

livvewran.-

0./1- Cona/Ivo A 0. M. CORBINO. TRANSFORMATION 0F POLYPHASE CURRENTS INTO PRACTICALLY CONSTANT DIRECT CURRENTS.

APPLICATION FILED IAN-7,19I8.

Pandsepn 13,1921.

2 SHEETS-SHEET 2.

UNITED lSTATES PATENT oFFlCE.

R80 MRIO CORBINO, 0F ROME, ITALY.

TRANBFOBIATION 0F POLYPHASE- CURREN'ilS INTO PRACTICALLY CONSTANT DIRECT CURRENTS. v

Specicaton of Letters Patent. Patented Sept. 13, 1921.

Application led January 7, 1918. Serial No.- 210,716.

` rents, of which the following is a full, clear,

and exact specification.

The' present invention refers to an apparatus for transforming alternating monophase or polyphase currents into practically constant direct currents, the transformation being accomplished in two successive steps.`

' In the first of said -steps the alternating monophase or polyphase currents are converted intounidirectional intermittent current, that is to say into a current constituted by the succession of separate impulses flowing all in the same direction whichare cyclically supplied by each of the phases, during a certain fraction of the'I complete wave. The duration of the said impulses, the choice of the particular fraction of the wave utilized, and the durations of the pauses between successive impulses are determined in such manner as to meet the requirements of the particular circumstances in each case.

In the second step the intermittent or pulsating current, generated at the first step,

is transformed into continuous direct current, of practically constant intensity. This result is obtained by partially storing in a potential form the energy of the successive unidirectional impulses supplied by the polyphase currents and then utilizing said stored potential energy in the form of a second set of unidirectional auxiliary impulses of currents, sent to fill (in the circuit which must be fed with continuous current) the gaps between the successive primary impulses proceeding directly from the original polyphase currents.

The method above described may be carried out in practice in a great variety 'of vMays, a few of which are herein disclosed by way of example and explained with reference to the annexed drawings, which refer more particularly to the case o'f the transformation of three-phase currents.

In the accompanying drawings:

Figurel 1 shows a converter for changing three-phase currents into unidirectional intermittent currents, said converter comprisingva rotary mercury jet interrupt/er.

1g. 2 shows an equalizer which by means of an inductance and a rectifier, fills up the gaps between the successive impulses of the mtermlttent current.

F ig. 3 is a diagrammatic view showing another form of converter and another form of equalizer, these being shown connected together as in use.

Fig. 4 shows the converter shown in Fig. 3, but slightly modified.

The apparatus for transforming alternatlng currents into practically constant direct currents comyrises' a converter A and an equalizer B. he converter, which is shown 1n F 1g. l, comprises a hermetically sealed vessel A2 in which there is an atmosphere either of hydrogen, of illuminatin gas, or of ether vapor. Mounted within t e vessel A2 which is cylindrical in form, are a plurality of electric contacts a, b, c, d, e andf operation is concerned, into two sets, one

set a, b, c being connected together and to the apparatus or net-work 7c which is to be fed by the continuous current produced, and the other set d, e, f being connected respectively to the terminals 1, 2 and 3 of the polyphase current to be converted and transformed.

In the vessel A2 of the converter there is provided a rotatable double nozzle tube g which is mounted to rotate about the axis of the cylindrical vessel and through the two nozzles of which mercury is adapted to flow in a radial direction toward the contacts a to f, so as to electricall connect, at intervals durmg the rotation o the nozzle, the contacts of one set with the diametrically opposite contacts of the other set. The arrangement is such that during the rotation of the mercu tube g the mercury jet impinges vsuccessively against the contacts d, e, f in the current from the contacts d e, f,vw ich will -be in only one direction but which. will be intermittent, as'will be well understood.

The tube g forthe mercury jet is rotated by means of a s nchronous motor which completes one-hal turn at each period of the alternations of the current, this motor being fed from the alternating current which it is desired to transform. Suitable means for causing the motor and the mercury to rotate in proper synchronism may be pro-v vided. K The duration of a connection ofthe mercury jet with the contacts d, e, f, may also be varied so as to lengthen or shorten the duration of the successi-ve impulses. This may be carried out b forming the contacts so that the taper, ,or instance triangular or trapezoi al form as shown in Fi 5,1and then providing for simultaneous ad]ustment of the contact transversely of the jet.

The continuous current net-work or apparatus lc is connected on one side,.as above stated, to the contacts a, b, c, by the wire k and on the other side it is connected to a neutral N in the alternating current network. If the latter net-work does not have a neutral, an artificial neutral may be provided by means of three-phase iron core and star-connection winding.

It will be noted that the mercury 'et inl its function in this system is lquite di erent from its ordinary function which is merely to provide for a quick make and break. In the present case its function is to act as a connection between two sets of contacts at intervals which are substantially constant in duration. I

As is above stated, the impulses given to the direct Acurrent net-work lc by the mercury jet and the contacts a, b, c, and d, e, f, follow each other successively, but there are gaps between these impulses which mustbe filled if a substantially continuous current is to be produced. These gaps are filled according to the present invention by supplementary impulses generated and suppliedto the direct current net-work by an equalizer B shown in Fig. 2. The equalizer comprises an inductance o and a current rectifier which may be in the form of an electrolytic cell V, aving an aluminum plate A1 and a lead plate I b immersed in solution of phosphate o f sod1um, phosphate of ammonium, or the like. The inductance o is arranged in series with the .direct current net-work indicated by a in Fig. 2, whatl the rectifier V is shunt vto facilitate or boost it by means 0f its o wn 'energy' and the condensation charge existing in the electrode of aluminum, when the flow of current ceases between th'e intervals of the impulses caused by the converter.

The function 'of the rectifier is to render completethe circuit outside the converter when it is momentarily interrupted to make possible the utilization of the stored energy.

The function of the inductance is to supply energy for maintaining the current dur ing the intervals of commutation of the converter, derivin such energy from the electro-magnetic eld which it has generated and which slightly diminishes during the brief p ausesl between two successive im;

pulses.

' The foregoin arrangements may be conveniently modi ed in order to secure several improvements and simplifications. Fi 3 shows the converter Av and the equa izer B both adapted for use with three-phase current.

As shown in Fig. 3, of the six contacts of the mercury jet interrupter, the contacts a b, e, are omitted leaving only the three d, e', f spaced at intervals of 120 and connected with the three terminals 1, 2, 3, of the three-phase line. The receiving network c, to-which leads the conductor h, is, as in the other-form, connected to the neutral. point N, at one end; but, at the other end instead of being attached to the three plates a, b, c, of 'the interrupter above described, is lconnected withthe interrupter casin p and thereby to the mercury of the jet w ich impinges upon said casing at one side while impingin upon one of the contacts e', d', f" at `t e other side.- Iny this way the periodic connection at every third of the'period, between the 'phase lines and the neutral, through the receiving'net-work,

steadiness in the intensity of the current circulating vin the receiving netework, a few turns o1 of the wire ,through which flows iron core o on which is wound the inducal@ 9, as indicated in Fig. 3, immediately fisestablished by one or the other of the the `intermittent current, are wound on the before said wire joins the branches that go to the valve V'and to the inductance o. The purpose of these turns o1 of wire is that of rendering available, not only part of the intrinsic energy of the current which circulates in the winding but also the mutual energy Mja', of the winding o and of the turns of vwire o-1 now added, in the circuit of the receiving net-work lc, Fig. 3, during the pauses or decrements, efficient of mutual induction and i, the intermittentcurrent (which arrives from the interrupter) at the moment the circuit is broken. The receiver may thus be fed during the pauses without the current z', which flows through the same, undergoing any perceptible diminution, and thus better securing the desired steadiness.

It should be understood that the rotary converter may be utilized, alone to produce an intermittent unidirectional current for any use, and likewise the equalizer may be utilized for rendering continuous, either pulsating or constant, any intermittent unidirectional current proceeding from any apparatus, evendifferent from the converter above specified and illustrated in the draw- 1n gThe type of rotary converter or interrupter shown in Fig. 3 in which a periodic closure of the circuit is made between a contact and the wall of the vessel has the advantage that by giving the contacts d', e', f an angular width less than but close to 60, the duration of the interval between the mo ment one of the jets leaves one of the contacts and the moment the diametricallyl opposite jet impinges upon the succeeding plate may be reduced at pleasure, even to the vanishing point.

The most suitable width of the plates must be determined experimentally, because experience has shown that the duration of the physical contact is slightly superior to that which might be inferred from the value of the angular width of the contacts, and that it is dependent also upon the nature of the gas filling the vessel. The final regulation may be made at the factory, or 1t may be effected on the apparatus by giving a trapezoid or triangular form to the contacts and adjusting them more or less, whereby the -width of the plate traversed by the jet varies in extent.

In proportion as the duration of the pauses is being reduced, the action of the valve V, (lead-aluminum), in the equalizer is modified, said valve being designed, as explained, to make constant the pulsating and periodically interrupted tension.

In fact the aluminum anode acts as a condenser of great capacity; and an ordinary condenser of equivalent capacity may be substituted for it.

When the pause is reduced to zero, or the M being the co' b overlapping in the periods of contacts, of two contacts with the jet is very brief, the action of the cells becomes practically unnecessary, and they may even be dispensed with. In order to render constant the current in the receiver, the inductance suffices in such case through its well-known proper-I ties, since in such case the current between the jet and the plates never falls. Arcs at reak are not formed within the vessel,vex cept those 4very weak ones due to the selfinduction of the line wire which goes to the plate, and which can eventuallyv be eliminated by arranging some small condensers y between each contactv and the casing. Hence the vessel need not be filled with inert gas, as illuminating gas, andthe apparatus can be made to work open, while containing common air.

When the jets separation from theplate is accompanied by a small arc at break, the plates may be covered externally (Fig. 5)-, with an insulating cover q, for instance, of porcelain, which viewed from the axis, projects beyond the plate over all its periphery for some little distance (Fig. 5). The short projection 0f porcelain, becoming covered with mercury, prolonge the plate metallically and the break 1s accomplished between mercury and mercury instead of between mercury and plate, that is, it preserves the latter from wearing away.

The vessels wall may be lined inside with a cylindrical covering of hard and insulating material, for instance of enameled orcelain, whether adhering to the cylin er or independent of it.

Claims:

1. Ay system for transforming alternating current into constant continuous current, comprising a converter of the mercury jet type for transforming the alternating cur# rent into unidirectional current; means for connecting said converter with a source of alternating current; means for conducting the converted current from the converter for utilization; and an equalizer 'for delivering current between the successive impulses of the intermittent unidirectional current.

2. In a system for transforming polyphase alternating current into constant continuous current, a converter comprising an hermeti cally closed receptacle containing an inert gas, a rotating mercury jet in said receptacle, said jet throwing mercury in opposite directions, and contact plates arranged at uniform angular intervals inside said receptacle; means for connecting said plates with a source of alternating current; means for conducting the converted current from the converter for utilization; and an equalizer for supplying current between the successive impulses of the intermittent unidirectional current.

3. A system for transforming polyphase alternating current into constant continuous current, as speclfied in claim 2, 1n,Wh1ch the equalizer comprises an inductance and are-- ceiving apparatus connected in series in the unidirectional current circuit, and a valve, in parallel With said inductance and receiver, to open the local circuit when the inductance supplies current between the main impulses of the unidirectional current, and to close said local circuit when the main impulses are received.

5. `"A system for transforming polyphase alternating current into constant continuous current, as specified in claim 2 in which the equalizer comprises an inductance and a valve, each on respectively parallel branches of the conductor for the converted current, said nductance constituted by a winding of its branchy on an iron core and an auxiliary `winding over said first Winding and consisting of a few turns ofthe conductor for the converted current lin its part preceding the branching point.

6. A system for transforming three-phase alternating current into constant continuous current, as specified in claim 2, in which the converter comprises an hermetically closed receptacle, the body of which is conductive and forms part of the circuit, three contact plates at angular intervals of 1200 connected to a source of three-phase current, a conductor connecting said body with a current receiver, anda double mercury jet, revolving once every two periods and alternately and successively connecting one of the lates to the mercury in the receptacle and t ence to the body.

7. A system for transforming polyphase alternating current into constant continuous current, as specified in claim 2, in which the plates are substantially trapezoidal in shape so as to vary the length of contact with the mercury.

In testimony whereof I aiiix mysignature in the presence of twonwitncss'es'.

Rome, this 27th day of November, 1917.

ORSO MARIO OORBINO.

Witnesses:

Lm'rANo CHaBocn'rrA, AUGUSTO EGGENSCHWILER. 

